Unexpected partial flooding of basements has been observed to lead to a peculiar accident causing situation where considerable damage to several different heating system boilers is known to have occured. More importantly, the set of conditions which causes the problem is not of isolated or exceptional origin, because these conditions have repeatedly taken place in different settings with widely different kinds of gas-fired heating systems. In one incident, the fire department was summoned by tenants of an apartment building and the firemen encountered "fire popping up all over the place", meaning on the surface of the water which had flooded the basement as the result of heavy downpour rain. In addition, the heating system wiring (particularly the low-voltage thermostat wiring) was heavily damaged and the plastic knob and other parts on the combination gas valve/regulator body had melted. The fire department appeared to have no idea of what had gone wrong, and they merely concluded that the hot-water (hydronic) boiler had broken down. In another occurrence involving a different location and a steam-boiler of totally different design the same mysterious failing again took place. Just as in the previous situation, the gas valve was destroyed by intense heat where all the plastic parts had melted and the wires connected to it were charred. Again, and to my surprise, no one from the gas utility company (who was called to repair it) appeared to have any idea whatsoever of what had gone wrong: just that the basement had flooded and as a result the gas valve has "failed" and needed replacement.
Upon more careful examination and subsequent evaluation of the setting for each of these unsual failures, the common thread which has been discovered is that the water level which was observed to have been flooding each of the heating system boiler areas had been relatively shallow, on the order of 4 to 6 inches or so. I have since determined that what appears to take place is that natural gas is injected directly into the water in the form of gas bubbles which will then surface and ignite, either from being near the gas burner's pilot flame, or from one-another (like a "row of dominos"). This scenario is obviously the setting for a very dangerous situation, because the burning gas bubbles can at best merely damage the boiler and its controls, but worse they may ignite nearby flammable material or trash.
What I further discovered is that when the water floods and submerges the heating system's gas burner to a certain (albeit unexceptional) CRITICAL LEVEL, which happens to be typically on the order of 4 to 6 inches or so, the depth of the water is just sufficient to obstruct the main jets on the gas burner, while the pilot light and the associated thermocouple is ordinarily placed a little higher and keeps on operating as though nothing is wrong. This critical level for the floodwater establishes a set of conditions which uniquely combine to fool and thus defeat the usual safety provisions inherent of the modern gas valve used on the gas burner, because the still heated thermocouple continues to produce an interlock signal indicating that all of the operating conditions are proper, while in reality the actual operating conditions are not. As a result of this false thermocouple produced interlock signal condition, the main jets will be able to turn ON and massive amounts of gas will inject directly into the water as gas bubbles. Of course, if the water becomes deeper than the critical level the pilot light will also be snuffed out allowing the thermocouple to cool and a loss of the interlock signal, and the main gas valve can not open as provided for with the usual safety precautions included by most, if not all, gas valve manufacturers. Unfortunately the water level invariably has to pass through the certain critical level where false operation of the burner occurs if the heating system or hot water heater calls for "more heat". This condition is of course more exacerbated in cold weather or during certain portions of the day when main burner operation is likely to be more frequent.
I find that it is the surfacing gas bubbles which lead to the peculiar distruction of the burner's gas valves and wiring. If a typical gas burner setup such as commonly found in a boiler or furnace is investigated, it is usual that the main gas jets are quite near (and often under) the gas valve. It is also usual practice that the main gas jets are sited substantially lower than the location of the pilot light and thermocouple. As a result, any gas which becomes injected into the water may surface under or very near the valve and where it can be ingnited by the still-burning pilot flame. Obviously much damage will result from such a situation. It is also possible that, if the gas bubbles are to drift some distance away from the gas burner before they surface and ignite, the even more dangerous possibility is present for further igniting of nearby inflammable trash or other objects. A worst-case scenario is that of where the raw gas accumulates in the confined area of a basement or boiler room and is then suddenly ignited by the still-present pilot light flame with the result being a massive explosion or building fire.
The current design and manufacture method of modern gas burners used in boilers and furnaces is a clearly defined area of at least engineering oversight, if not outright product negligence. It is probably unknown just how many fires, explosions, and deaths occur each year due to the synergistic effect of shallow flooding of a basement causing partial gas burner flooding to a critical level which leads to failure of the usual safety provisions of a conventional gas burner. For the most part, in the event of severe fire or explosion, the cause may be written-off as due to unknown causes. Product negligence results because popular and well-known manufacturers of gas-fired major appliances such as furnaces and boilers continue to make and sell huge quantities of equipment which does not provide any shut-down provision for the gas burner apparatus in the event of partial flooding such as I have observed to occur. Moreover these same manufacturers do not provide for any aftermarket retrofit of millions of not-so-old existing installations in homes and commercial buildings.